A junction-free copper reference electrode for electrochemical measurements in o-nitrophenyl octyl ether

A freshly polished copper wire immersed into the o-nitrophenyl octyl ether (o-NPOE) solution of a supporting electrolyte was used as a junction-free reference electrode (RE) in electrochemical measurements at the metal ∣ o-NPOE and water ∣ o-NPOE interfaces. Its stability and reliability were examined by measurement of the half-wave potentials (E1/2) of ferrocene oxidation on the Au and Pt electrodes, and of transfer of a series of tetraalkylammonium ions across the water ∣ o-NPOE interface. The potential of the Cu RE was found to be stable to within ±0.002 V over a period of time longer than 300 h. The small size, simple preparation and conditioning predetermine the electrode for applications requiring the miniaturisation of the electrochemical set-up.